Jason McLennan says green building is not about putting on a sweater when you’re cold. It is about creating better buildings. For two decades, his mission has been helping the design and construction industry do just that.

Best known as the author of the Living Building Challenge (LBC), a certification system that is widely regarded as the world’s most stringent green building standard, McLennan, now 42, started his architecture career at the pioneering sustainablearchitecture firm BNIM in Kansas City, Missouri. In 2004, he became its youngest partner. But in 2006, hoping to push green architecture further, he left to become CEO of the Cascadia Green Building Council, the Pacific Northwest chapter of the U.S. Green Building Council. From there, he officially launched the LBC. Three years later, he founded the International Living Future Institute (ILFI).